Diazonium compounds and diazotype materials containing them

ABSTRACT

New light-sensitive benzene diazonium compounds are provided, which have a halogen atom in an ortho position relative to the diazonium group, an alkylthio in meta position and a dialkyl, alkylcycloalkyl or alkylaralkyl tertiary amino group in para position. These compounds are especially useful in one-component diazotype materials to be developed by liquid phloroglucinol developers, as they have high coupling activity and they form images of black or dark brown azo dyestuffs having light backgrounds, improved water fastness and high absorptiveness to ultraviolet radiation.

United States Patent 1191 Hendriks et al.-

[ DIAZONIUM COMPOUNDS AND DIAZOTYPE MATERIALS CONTAINING THEM [75] lnventorsz Mathieu J. M. Hendriks, Tegelen;

Gerardus J. Crommentuyn, Lottum, both of Netherlands [73] Assignee: Oce-van der Grinten N.V., Venlo,

Netherlands [22] Filed: June 1, 1971 211 App]. No.; 148,954

[30] Foreign Application Priority Data A June 19, 1970 Netherlands 7009028 [52] US. Cl 96/91 R, 96/49, 96/75,

260/ 141 [51] Int. Cl G03c 1/54, C07c 113/04 [58] Field of Search 96/91 R, 75, 49; 260/141-,"142

[56] References Cited v UNITED STATES PATENTS 3,615,578 10/1971 l-lectors et a1 96/91 R 3,300,471 1/1967 Arrigo 96/91 R X 3,407,066 10/1968 Mustacchi et al 96/91 R 3,442,650 5/1969 Hendrickx et a1. 96/91 R 3,442,651 5/1969 l-lendrickx et a1. 96/91 R 3,442,652 5/1969 Hectors et a1 96/91 R Nov. 27, 1973 3,169,869 2/1965 l-lendrickx 96/75 X 2,286,701 6/1942 Werner 3,281,246 10/1966 Rauhut et a1. 3,459,550 8/1969 Munder et al. 2,990,281 6/1961 Printy et a1. 96/91 R X FOREIGN PATENTS OR APPLICATIONS 919,037 2/ 1963 Great Britain 96/91 R OTHER PUBLICATIONS Noller, C., Textbook of Organic Chemistry", 2nd Ed., W. B. Saunders Co., p. 341.

Primary Examiner-Charles L. Bowers, Jr. Att0rney-A1bert C. Johnston [57 ABSTRACT New light-sensitive benzene diazonium compounds are provided, which have a halogen atom in an ortho position relative to the diazonium group, an alkylthio in meta position and a dialkyl, alkylcycloalkyl or alkylaralkyl tertiary amino group in para position. These compounds are especially useful in one-component diazotype materials to be developed by liquid phloroglucinol developers, as they have high coupling activity and they form images of black or dark brown azo dyestuffs having light backgrounds, improved water fastness and high absorptiveness to ultraviolet radiation.

6 Claims, No Drawings 1 DIAZON IUM COMPOUNDS AND DIAZOTYPE MATERIALS CONTAINING THEM The present invention relates to new diazonium compoundsand to diazotype material made by use of these compounds. The diazotype material may be a one component diazotype material to be developed with a liquid containing an azo component, a two-component diazotype material to be developed with gaseous or liquid alkali, or heat-developable diazotype material.

Among the requirements fordiazonium compounds for sensitizing diazotype material are that they have adequate light-sensitivity, good stability and adequate coupling activity; that their photo-decomposition products be and remain completely or almost completely colorless; and that with usual azo-coupling components they will form stable high-contrasting azo dyestuffs having good water-fastness and also often having high absorption for ultra-violet copying light. Further, .the azo dyestuff should'be resistant to bleeding during development. v

Among the light-sensitive benzene diazonium compounds often used for sensitizing diazotype material are those which have a tertiary amino group in the para position and an etherified hydroxyl group in the meta position, and possibly a further substituent suchas halogen, alkoxy or alkyl in' the ortho position, relative to the diazonium group. Compounds of this type are described in British Patent Specifications 888,598, 919,037, 1,081,274 and 1,112,543.

Diazotype material sensitized with diazonium compounds according to the said British patent specifications is generally of good quality. For various uses, however, further improvement is needed. For example, when using weakly acid buffered solutions of phloroglucinol as a developer the coupling activity (developing speed) of theknown material sometimes lies below the desired level. Moreover, the absorption of ultra violet light by the dyestuffs formed from the'known diazonium compounds is susceptible of improvement. This tri-fluoromethylphenyl or-a cyanophenyl group. Any of the substituents R R and R may carry one or more further substituents of kinds commonly known to be useful in diazonium compounds for diazotype materials.

Surprisingly it has been found that the diazonium compounds according to this invention have a higher coupling activity than the similar known diazonium compounds from which they differ structurally only by the presence of a sulphur atom instead of an oxygen atom in the meta position relative to the diazonium group. ln the same surprising way, diazotype materials making use of these new diazonium compounds have been found to show a much smaller tendency to bleed during development than diazotype materials making use of the most similar known diazonium compounds, and the dyestuffs formed by development of them have not only a considerably higher water-fastness but also better absorption for ultra violet radiation than do those formed from the most similar known compounds.

The present diazonium compounds are also very light-sensitive and they have good stability. Upon development with azo-coupling components conventionally used in the diazotype art they yield dark dyestuffs, of which the shade varies from dark-brown to black de pending upon the particular diazonium compound and azo-coupling component used and upon the acidity of the developing liquid. The dyestuffs formed are stable. The photo-decomposition products in the completely exposed background are colorless or almost colorless.

The new diazonium compounds according to the invention are generally used in diazotype material in the form of their metallic salts. Examples of the basic new compounds are: 4diazo 3-chloro Z-methylthio-N,N-dimethylaniline 4-diazo 3-chloro 2-ethylthio-N,N-dimethylaniline is important for uses of the compounds in transparent diazotype materials.

The present invention relates to new diazonium compounds and also to diazotype material made by use of them, which have several properties that areconsiderably improved as compared with the corresponding properties attained 'by said known diazonium compounds.

According to this invention, diazonium compounds are provided which conform to the general formula NaX in which X represents an anion, Z is a halogen atom occupying an ortho-position with" respect to the diazonium group, R is an alkyl, group, whether or not branched or saturated, orapara-substituted phenyl group, R is an alkyl group, and R is an alkyl group, whether or not'branched, or a cycloalkyl or aralkyl group.

When the thio'substituent R is a para-substituted phenyl group, it maybe a chlorophenyl, methylphenyl,

d-diazo 3-chloro 2-n-propylthio-N,N-dimethylaniline 4-diazo 3-ch loro 2-isobutylthio N,N-dimethylaniline 4-diazo 3-chloro 2-al lylthio-N,N-dimethylaniline 4-diazo 3-chloro Z-ethyIthio-N-methyl-N- cyclohexylaniline 4-diazo 3-fluoro 2(4'-chlorophenyl)thio-N,N- dimethylaniline I 4-diazo 3-chloro 2(4'-chlorophenyl)thio-N,N- dimethylaniline 4-diazo 3-bro mo 2(4-chloropheny-l)thio-N,N-

dimethylaniline 4-diazo 3-chloro 2(4'-methylphenyl)thio-N,N- dimethylaniline 4-diazo 3-chloro 2(4'-trifluoromethylphenyl)thio N,N-

dimethylaniline 4-diazo 3-chloro 2(4'-rnethylphenyl)thio-N-methyl-N- cyclohexylaniline 4-diazo 5-chloro 2(4'-cyanophenyl)thio-N,N- dimethylaniline 4-diazo S-chloro 2(4'-chlorophenyl)thio-N,N- dimethylaniline 4-diazo 5-chloro 2-ethylthio-N-methyl-N-benzylaniline 4-.diazo S-chloro 2(4-chlorophenyl)thio-N-methyl-N- (2',6'-dichlorobenzyl)aniline.

The new compounds can be used in diazotype material individually, mixed together, or mixed with diazonium compounds of other types. Their specific advantagesare of. course attained to a lesser degree as the content'of diazonium compounds of other types increases.

The diazonium compounds can be employed in sensitizing solutions applied to conventional diazotype support materials such as paper, translucent paper, printing-plate paper, transparent cloth, opaque cloth, synthetic paper, metal sheets, glass fibre, polyester film, and the like. They may also be incorporated in a hydrophilic or hydrophobic film layer.

Those of the new compounds which have a light dialkylamino group in the para position and a light alkylthio group in the meta position, each alkyl constituent containing up to two carbon atoms, are particularly suitable for use in two-component diazotype material.

Those of the new diazonium compounds which have in the para position a heavier dialkylamino group containing three to six or more carbon atoms in at least one of the alkyl constituents, or an N-alkyl-N-aralkylamino or N-alkyl-N-cycloalkylamino group, or which have in the meta position an alkylthio group containing three to six or more carbon atoms or a para-substituted phenylthio group, are especially suitable for use in onecomponent diazotype layers.

The materials having a one-component diazotype layer can be developed by the application of a liquid containing an azo-coupling component, which liquid may be alkaline or weakly acid and may be buffered at the desired pH.

Particularly advantageous diazonium compounds according to the invention are those which carry in successive vicinal positions a diazonium group, achlorine atom, a parasubstituted phenylthio group and a dialkylamino group each alkyl constituent of which contains at most two carbon atoms. Upon development with weakly acid buffered phloroglucinol developers diazotype materials sensitized with these compounds yield copies having images of azo dyestuffs which appear to be and are regarded as black diazotype images. Copies having deep brown azo dyestuff images are obtained with the use of conventional alkaline phloroglucinol developers.

Conventional auxiliary agents can be used in the diazotype material according to the invention. Examples of such agents are acids such as citric acid, tartaric acid and boric acid; stabilizers such as benzene and naphthalene sulfonic acids, p-phenol-sulfonic acid and their water-soluble salts; metal salts such as zinc chloride, magnesium chloride, nickel sulfate and alum; materials which serve to increase the developing speed, such as glycerol, polyethyleneglycol, urea, thiosinamine, and the like; surface improving substances such as finely powdered silicon dioxide (colloidal or non-colloidal), aluminum oxide, barium sulfate, rice starch, etc.; binders such as gelatin, gurn arabic, cellulose ethers, starch derivatives, polyvinyl alcohol, and dispersions of synthetic polymers such as cationic, non-ionic and anionic polyvinyl acetate dispersions; and substances which serve to stabilize the background of the copies, such as thiourea.

The phloroglucinol developers used for onecomponent diazotype material often vary with regard to their composition and acidity. Following are the compositions of two weakly acid phloroglucinol developers and one weakly alkaline phloroglucinol developer which are used commercially and are employed for development in a number of detailed examples of the invention:

Developer A is a solution of 4 g of phloroglucinol 0.1 g of acetoacetanilide 3 ml of 2-ethylhexyl sulfate 15 g of beet sugar 2.5 g of benzoic acid 14 g of sodium benzoate and 135 g of sodium formate in 1,000 ml of water. The pH of this liquid is approximately 5.8. Developer B is a solution of:

6.5 g of phloroglucinol 4 g of resorcinol 10 g of thiourea 2 g of the sodium salt of dibutylnaphthalene sulfonic acid 14 g of sodium benzoate 49 g of trisodium citrate (2 aq.) and 1.2 g of citric acid in 1,000 ml of water. The pH of this liquid is approximately 6.5. Developer C is a solution of:

30 g of thiourea 5.4 g of phloroglucinol 6.5 g of resorcinol 1 g of potassium salt of hydroquinone monosulfonic acid 5 g of sorbitol 15 g of beet sugar 50 g of potassium tetraborate (5 aq.) and 1.5 g of the sodium salt of isopropylnaphthalene sulfonic acid in 1,000 ml of water. The pH of this liquid is approximately 9.

EXAMPLE I A. A sheet of white diazotype base paper of weight g/m is sensitized with a liquid containing 25.7 g of 4-N,N-dimethylamino-3(4'- chlorophenyl)thio-6-chlorobenzene diazonium chlorozincate 5 g of tartaric acid and 30 ml of aqueous polyvinyl acetate dispersion (Vinnapas H 60 manufactured by Wacker-Chemie G.m.b.l-l., Munich, Germany) in 1,000 ml of water, and the paper then is dried.

B. Another sheet of the same white base paper is sensitized with a liquid containing:

24.7 g of 4-N,N-dimethylamino-3(4- chlorophenoxy)-6-chlorobenzene diazonium chlorozincate 5 g of tartaric acid and 30 ml of aqueous polyvinyl acetate dispersion (Vinnapas H 60) in 1,000 ml of water, and then is dried.

The two diazotype papers A and B are very lightsensitive. Paper A has a higher coupling activity than paper B. I

Strips of the two papers are separately exposed under a transparent ink drawing until the diazonium compound has bleached out completely beneath the blank portions of the drawing. The two strips are then developed with developer B, dried, subsequently immersed in water and dried in vertical position. The copies thus obtained show a very dark image on a white background. However, the dyestuff of diazotype paper B.

was spread over the white background, whereas the dyestuff of diazotype paper A shows no appreciable bleeding, proving that it has an excellent waterfastness.

The diazonium compound used in paper A was prepared as follows:

By reaction with para-chlorobenzene-thiol and potassium hydroxide,v 2,5-dichloronitrobenzene was converted into 2(4'-chlorophenyl)-thio-5- chloronitrobenzene. The nitro group of this product was reduced to an amino group. The amino group was tosylated. The product thus obtained was nitrated to 2-(4 -chlorophenyl )thio-4-nitro-5-chloro-N- tosylaniline, whereupon the tosylamino group was methylated, saponified, and methylated again. From the 2-(4'-chloro-phenyl)thio-4-nitro 5-chloro-N,N- dimethylaniline thus obtained, the diazonium chlorozincate was obtained by reduction and diazotation in the usual way. A

EXAMPLE II A natural tracing paper is used that weighs 80 'g/m and is coated with a cellulose acetate layer weighing approximately 20 g/m, which has been superficially hydrolysed to a depth of about 4 microns and washed out with water in order to remove the chemicals used for the hydrolysis. This paper is sensitized with a solution containing:

' 64.3 g of 4-N,N-dimethylamino-3(4'- chlorophenyl)thio 6-chlorobenzene diazonium chlorozincate 9.3 g of tartaric acid 18.6 g of potassium aluminum sulfate (24 aq) and 200 ml of propanol in 800 ml of water, and then is dried.

A sheet of the diazotype material thus obtained is marked A.

Another sheet of the same tracking paper is sensitized with a solution as described above except that, instead of 64.3 g of the named compound according to the invention, an equimolar quantity of 4-N,N- dimethyl-3-(4'-chloro-phenoxy)-6-chlorobenzenev diazonium chlorozincate is used; and then it is dried. This sensitized sheet, marked B, contains the same molar quantity of diazonium salt per square meter as sheet A.

The two sheets are separately exposed under the same transparent step-wedge until under the lightest step of the wedge all the diazonium compound has just bleached out. Then the two sheets are developed with developer B.

From the first intermediate copies thus obtained, by transmission of U.V. light through them, second intermediate copies are made identically on two identical sheets of diazotype paper. The second intermediate copy obtained with the use of sheet A has a much higher density of azo dye inits darker portions than does the second intermediate copy obtained with sheet B. correspondingly, the azo dyestuff on sheet A absorbs the ultra-violet light better than that on sheet B. The diazonium compound used on sheet A was prepared in conformity with the method of preparation described in Example 1.

EXAMPLE 111 A. A sheet of white base-paper of weight 80 g/m is sensitized with a liquid containing:

26.1 g of 4-N,N-dimethylamino-3-isobutylthio-2- chloro-benzene diazonium chlorostannate 5 g of tartaric acid and Y 30 ml of aqueous polyvinyl acetate dispersion (Vinof the drawing. Each strip is then developed with develnapas H 60) in 1,000 ml of water, and then is dried.

B. Another sheet of the same paper is sensitized with a liquid containing:

oper B with the use of smooth rollers.

The image obtained with diazotype paper B is black on a white background, but the dyestuff formed has bled during development. The image obtained with diazotype paper A is bluish black and shows hardly any bleeding. The diazonium compound used in paper A was prepared as follows:

By reaction with isobutanethio] and potassium hydroxide, 2,3-dichloronitrobenzene was converted into 2-isobutylthio-3-chloronitrobenzene. The nitro group was reduced to an amino group and this latter group tosylated. The product thus obtained was nitrated to 2-isobutylthio3-chloro-4-nitro-N-tosylaniline; the tosylamino group of which was subsequently methylated, saponified, and methylated again. From the 2- isobutylthio-3-chloro-4-nitro-N,N-dimethylaniline thus obtained the diazonium chlorostannate was obtained by reduction and diazotation in the usual way.

EXAMPLE iv A sheet of super-calendered paper of weight g/m is coated with a dispersion of the following composition:

,500 ml of a solution of 66 g polyvinyl alcohol having a degree of hydrolysis of 99.8 percent in 1,000 ml of water 200 ml of an aqueous dispersion of 730 g per liter titanium dioxide which has been additionally treated with A1 0 and SiO and has an average particle size of about 0.2

1 ml of water glass 81 ml of a 40 per cent glyoxal solution in water and 55 ml of isopropanol in 163 ml of water.

The layer is dried and hardened by heating it for 10-20 seconds at l55-l 60C. It weighs approximately 12 g/m in dry condition.

The material thus obtained is sensitized with a solution of:

24.5 g of 4-N,N-dimethylamino-3-(4'-methylphenyl) thio-2-chlorobenzene diazonium chlorozincate 4.2 g of tartaric acid and 200 ml of ethanol in 800 ml of water, and then is dried.

A positive-working light-sensitive planographic printing plate is thus obtained. This plate is imagewise exposed under a text typed on tracing paper, until the diazonium compound has bleached out completely under the blank portions of the original. Subsequently, the light-sensitive side of the plate is developed'by rubbing it with a solution containing:

12 g of phloroglucinol l5.3 g of citric acid 87 g of disodium phosphate (2 aq.)

50 g of sodium chloride and 50 ml of propanol in water up to 1,000 ml.

After the development the plate is sponged off with water. It then shows a brown image on a white background. By the use of this plate at least 200 good positive prints can be obtained in an offset printer.

The diazonium compound used in the example was prepared as follows:

By reaction with para-toluenethiol and potassium hydroxide 2,3-dichloro-nitrobenzene was converted into 2-(4-methylphenyl)thio-3-chloronitrobenzene. The nitro group was reduced to an amino-group, and the latterwas tosylated. The product so obtained was nitrated to 2-(4'-methylphenyl) thio3-chloro-4-nitro-N- tosylaniline, which was methylated, saponified, and methylated again. From the 2-(4-methyl-phenyl)thio- 3-chloro-4-nitro-N,N-dimethylaniline thus prepared the diazonium chlorozincate was obtained in the usual way by reduction and diazotation.

EXAMPLE V A sheet of super-calendered paper of weight 105 g/m is coated in the same way as described in Example IV and subsequently is sensitized with a solution of:

25.3 g of 4-N-methyl-N-benzylamino-3-ethylthio-6- chlorobenzene diazonium chlorozincate 4.2 g of tartaric acid and 200 ml of ethanol in 800 ml of water.

The positive-working light-sensitive planographic printing plate thus obtained is imagewise exposed under a text typed on tracing paper, until the diazonium compound has bleached out completely under the blank portions of the original. After development in the way and with the developer described in Example IV, a plate showing a dark brown image on a white background is obtained.

With the use of this plate at least 200 good positive prints can be obtained in an offset printer.

The diazonium compound used in the example was prepared as follows:

By reaction with ethanethiol and potassium hydroxide 2,5-dichloronitrobenzene was converted into 2- ethylthioS-chloronitrobenzene. The nitro group was reduced to an amino group, which was then tosylated. The product so obtained was nitrated to 2-ethylthio-4- nitro-5 chloro-N-tosylaniline, the tosylamino group of which was methylated, saponified and benzylated. The 2-ethylthio-4-nitro-5-chloro-N-methyl-N-benzylaniline thus obtained was converted into the diazonium salt in the usual way by reduction and diazotation.

EXAMPLE VI White base-paper of weight 80 g/m is sensitized with a solution containing: I

25.7 g of 4-N,N-dimethylamino-3(4'-chlorophenyl) thio-2-chlorobenzene diazonium chlorozincate 5 g of tartaric acid and 30 ml of aqueous polyvinyl acetate dispersion (Vinnapas H 60) in 1,000 ml of water, and then is dried. The one-component diazotype material thus obtained is imagewise exposed under a transparent ink drawing until the diazonium compound has bleached out completely under the blank portions of the drawing. It is then developed with developer A.

The copies obtained show a brownish black image on a white background.

The diazonium compound used in this example was prepared as follows:

2,3-dichloronitrobenzene was converted into 2(4'- chlorophenyl)thio-3-chloronitrobenzene by conversion with parachlorobenzenethiol. The nitro group was reduced to an amino group and this latter group was tosylated. The product so obtained was nitrated to 2-(4'- chlorophenyl)thio-3-chloro-4-nitro-4-tosylaniline. The tosylamino group of which was methylated, saponified, and methylated again. From the 2-(4- chlorophenyl )thio-3-chloro-4-nitro-N ,N- dimethylaniline thus obtained the diazonium salt was obtained in the usual way by reduction and diazotation.

EXAMPLE VII Sized natural tracing paper of weight g/m is sensitized with a liquid containing:

60 g of 4-(N-methyl-N-cyclohexyl)amino-3(4- methyl-phenyl)thio-2-chlorobenzene diazonium chlorostannate 5 g of tartaric acid and 200 ml of propanol in 800 ml of water, and then is dried.

A sheet of the sensitized paper, which is very light sensitive and transparent, is imagewise exposed under a transparent ink drawing until the diazonium compound has bleached out completely under the blank portions of the drawing. It is then developed with developer C. The copy obtained shows a dark brown image on a clear background. This copy is very well suited for making further copies on diazotype material.

The diazonium compound used in this example was prepared as follows:

The 2(4methylphenyl)thio-3-chloro-4-nitro-N- tosylaniline obtained from 2,3-dichloronitrobenzene according to Example IV was methylated, saponified, and cyclohexylated. The 2-(4'-methylphenyl)thio-3- chloro-4-nitro-N-methyl-N-cyclohexylaniline so obtained was converted into the diazonium salt in the usual way by reduction and diazotation.

EXAMPLE VIII l5.8 g of 4-N,N-dimethylamino-3-methyIthio-2- I chlorobenzene diazonium chlorostannate 30 g of tartaric acid 5 g of boric acid 30 g of l,3-dihydroxy-4-((2-hydroxyethyl)amino) carbonylbenzene and 30 ml of isopropanol in 1,000 ml of water, and then is dried.

The two-component diazotype paper thus obtained is imagewise exposed under a transparent ink drawing until under its blank portions the diazonium compound has bleached out completely. It is then developed in ammonia vapor. The copy obtained shows a contrasty brown image on a clear background.

The diazonium compound used in this example was prepared as follows:

By reaction with methanethiol and potassium hydroxide 2,3-dichloronitrobenzene was converted into Z-methylthio-3-ehloronitrobenzene. The nitro group was reduced to an amino group which was then tosylated. The product thus obtained was nitrated to 2- methylthio-3-chloro-4-nitro-N-tosylaniline, the tosylamino group of which was subsequently methylated, saponified, and methylated again. From the 2- methylthio-3-chloro-4-nitro-N,N-dimethylaniline thus obtained the diazonium salt was obtained in the usual way by reduction and diazotation.

The invention is not to be construed as limited to the particular forms disclosed herein, since these are to be regarded as illustrative rather than restrictive.

We claim:

1. A diazonium salt of the formula in which X represents an anion, Z is a fluorine, chlorine or bromine atom in an ortho position relative to the diazonium group, R is an alkyl group having one to six carbon atoms, R is an alkyl group having one to six carbon atoms, and R an alkyl group having one to six carbon atoms or a cyclohexyl or benzyl group.

2. A diazonium salt according to claim 1 carrying in successive vicinal positions a diazonium group, a chlorine atom, an alkylthio group and a dialkyl-amino group each alkyl constituent of which contains at most two carbon atoms.

3. A diazonium salt according to claim 1, selected from the group consisting of chlorozincate, 4- dimethylamino-3-isobutylthio-2-chloro benzene diazonium chlorostannate, and 4-(methyl-ben'zyl)amino-3- ethylthio-G-chloro benzene diazonium chlorozincate.

4. One-component diazotype material comprising a support having thereon a coating comprising a lightsensitive diazonium salt according to claim 1 in the substantial absence of an azo coupling component.

5. One-component diazotype material comprising a support having thereon a coating comprising a lightsensitive diazonium salt according to claim 2 in the substantial absence of an azo coupling component.

6. One-component diazotype material comprising a support having thereon a coating comprising a lightsensitive diazonium salt according to claim 3 in the substantial absence of an azo coupling component. 

2. A diazonium salt according to claim 1 carrying in successive vicinal positions a diazonium group, a chlorine atom, an alkylthio group and a dialkyl-amino group each alkyl constituent of which contains at most two carbon atoms.
 3. A diazonium salt according to claim 1, selected from the group consisting of chlorozincate, 4-dimethylamino-3-isobutylthio-2-chloro benzene diazonium chlorostannate, and 4-(methyl-benzyl)amino-3-ethylthio-6-chloro benzene diazonium chlorozincate.
 4. One-component diazotype material comprising a support having thereon a coating comprising a light-sensitive diazonium salt according to claim 1 in the substantial absence of an azo coupling component.
 5. One-component diazotype material comprising a support having thereon a coating comprising a light-sensitive diazonium salt according to claim 2 in the substantial absence of an azo coupling component.
 6. One-component diazotype material comprising a support having thereon a coating comprising a light-sensitive diazonium salt according to claim 3 in the substantial absence of an azo coupling component. 